The WiFi sucks out past Pluto

Surprisingly the basic principles that satellites, rockets and all other form of spacecraft use to communicate with Earth is not overly different from your grandad's tube radio, or the cell signal in your mobile phone. In fact, all wireless communications operate on one simple guiding principle:

Take the information you need and stuff it onto an RF carrier wave

Admittedly I have simplified a great deal in that one line, but lets unpack that statement with an example we should all know from high school - analogue FM radio (it makes me feel old that I need to specify analogue).

FM radio is fairly simple - you take a centre (carrier) frequency and increase it or decrease it in order to simulate the shape of a sound wave.

As you can see, my art skills have broadened to include complex scientific diagrams

This process is called frequency modulation (or FM, hah!). FM radio solves the problem of people not being able to effectively shout at each other over long distances. The process is (relatively) simple. You take your information (in this case sound) and you stuff it (modulate it) into an RF carrier wave (104.1MHz, or whatever radio station takes your fancy).  

The steps to send digital data using modulation schemes like this then isn't that much of leap. Digital data is literally all just 1s and 0s. Using frequency modulation, we can set some high frequency to represent a 1 and some low frequency to represent a 0. The receiver then detects shifts between high and low frequencies and turns this into a stream of bits which is all digital data is. This is called frequency shift keying, or FSK, and is the simplest form of modulating digital data so that it can be sent wirelessly. 

Thank you ezefranca and github

There are many more sophisticated and useful ways of modulating digital data but lets not get into that for now.

So... why do we encode things on RF carrier waves? Why not just send 1s and 0s directly? The reason we do this is because it allows us to reliably send that information over very long distances without having to rely on any medium. Electromagnetic waves go everywhere and can even go through many things. This means we can send data from as far away as Pluto, without having to build a huge data cable. The result are some pretty digital photos of a red loveheart that make it to the front page of Reddit. 

That is, so long as the person transmitting has decent technology and the person receiving has decent technology. And making technology decent is where some engineering magic happens.

Be strong, focus, drown out the noise

Lets say that we've gone back to pre-historic times where no one is transmitting any radio waves. You might think that if you stuck an antenna out and listened for transmissions, you'd 'hear' dead silence. Instead, you get this:

This image is from a website that sells white noise generating machines. Weird

White noise. It's everywhere. It's that static you hear when you don't have radio reception in your car. And it makes trying listening to radio waves an eternally annoying exercise. See if the radio waves you're trying to listen to are too weak, you won't be able to tell the difference between it and white noise. 

MORE POWER

Yes, if you push more power out your transmission antenna, chances are the person receiving it will hear it more clearly. The basic sound metaphor is apt - the person shouting the loudest will come through more clearly. So the stronger your signal is, the more clearly it will cut through the noise. 

There is a problem with this - direction...ness. 

My handwriting is also pretty bad

See in the above image, you'd be pumping out all your power in all possible directions. That means that only a small fraction of the power is actually received by the stick figure who's interested. Everything else is just... wasted. That's why we need

MORE FOCUS

I drew lines. Lines are simple

Using the magic of antennas we can focus our transmissions. And now we're reaching what a lot of satellites actually do. Satellite's use some antenna black magic so that we can focus our radio wave beams over a really really narrow area. 

How narrow? Well remember New Horizons? That can focus it's antenna beam width to just 0.3 degrees. Tiny right?

Time for Maths!

Pluto (which is where New Horizons is, give or take several thousand kilometres) is about 4.7 billion kilometres from Earth. After some simple trigonometry, a 0.3 degree beam width means that it's antenna has a 'footprint' about 24.6 million kilometres in diameter. For reference, Earth has a diameter of 12.5 thousand kilometers.

I tried

Earth is a tiny, tiny spec, receiving a tiny tiny fraction of the radio power that  New Horizons is pushing out.

So... uh.... what can we do now?

More...smarter?

This is where the magic becomes a truly deep, dark shade of black. We can do freaky maths stuff to the signal coming in to figure out what is noise and what isn't noise, even when the noise is really really loud. And even if the signal is still crud and you can only extract out small bits of meaningful data, there's another layer of software magic that allows for error detection and correction and request for retransmissions.

It's one of those rare occasions where we can polish a turd radio signal and make it shine.

But that is magic for another story for another day, children.

Let's end with an photo of Pluto, transmitted via radio waves from 4.7 billion km away

Isn't that a nice photo?